In recent years, in order to perform analysis of trace amounts of substances such as proteins or nucleic acids with high accuracy and at high speed, microchannel chips have been used. The microchannel chips have an advantage of requiring smaller amounts of reagents and samples and thus are expected to be used in various applications including clinical inspection, food inspection, and environmental inspection.
In order to automate processing using the microchannel chip, providing a valve structure in the microchannel chip is proposed (refer to NPLs 1 and 2, for example).
NPLs 1 and 2 disclose microchannel chips which include passive valves for stopping liquid flow in a channel by using the surface tension of the liquid. In these microchannel chips, the cross-sectional area of the channel is rapidly increased at a site where it is desirable to stop the liquid flow. By doing so, it is possible to stop the flow of liquid in a channel by using the surface tension of the liquid, at a site where the cross-sectional area of the channel is rapidly increased.